Transcript 16 - Chianti Topics

ARIEL
Atmospheric Remote-sensing Infrared
Exoplanet Large survey
Emanuele Pace
Università di Firenze
Giusi Micela
INAF – Osservatorio Astronomico di Palermo
On the behalf of the ARIEL collaboration
1
ARIEL context
• Composition and structure of hundred(s) of
exoplanet atmospheres by IR spectroscopy
• Targets from gas giants (Jupiter- or Neptunelike) to super-Earths in the very hot to warm
zones of F to M-type host stars
2
Key questions
1. What are (exo)planets made of?
2. How did they form?
3. How do they evolve?
Ingredients:
• ~ 500 (exo)planets
E.g. ~ 340 Gas giants, ~ 80 Neptunes, ~ 80 Super-Earths & sub-Neptunes
• They transit
• They are hotter than ~ 500K, their star is brighter than K=9-9.5
ARIEL recipe
Probe their atmospheric chemistry & dynamics through VIS+IR transit
spectroscopy and photometry
3
Observational strategy
Differential transmission (transits) & emission (eclipse) spectroscopy
4
Observational strategy
• Day side spectra - eclipse
– Reflected radiation - Visible -NIR
– Thermal emission - IR
T < 1200 K – Reflected emission > Thermal emission
1.
2.
3.
Albedo
T-P profile
Chemistry
• Night side spectra – primary transit
– Transmitted spectrum – IR
1.
2.
3.
Upper atmosphere
Chemical composition
Temperature
5
Key molecules absorbing in IR
ExoMol
6
Design Drivers
• 450 M€ cost at completion to ESA
– Need to keep ESA contributions to minimum possible in many areas
– Contributions to payload (telescope, detectors)
– Operations time to no more than 3.5 years (nominal mission)
– Minimise launch costs by keeping S/C dry mass < 1000 kg
• Maximise number of targets that can be examined in mission life
– Maximise mirror size within feasibility constraints
– Maximise instrument throughput – minimum number of channels
and resolution needed for science
– Agile spacecraft pointing, large field of regard
7
Launcher
8
L2 orbit
9
Mission phases
10
Payload Module Functions
• Telescope (~1 meter class), passively cooled to < 80 K,
diffraction limit at ~ 3 mm
• Single spectrometer module with dual optical chains
providing R ~ 300 coverage from 1.95 – 7.8 microns on
single detector
• FGS system (redundant) which doubles as a NIR
photometer for stellar variability monitoring
• Common optical bench and structure to support both
the instrument boxes and the telescope primary mirror
• Thermal isolation from SVM via V-grooves and
isolating cryo-harnesses.
11
Architecture
12
Overview of Payload Module
13
14
Telescope Parameters
Parameter
Ch0 (1.95-3.9m)
Telescope f/number
Ch1(3.9-7.8um)
f/13.4 (for 0.9 diameter circular aperture)
Entrance pupil diameter
Plate scale at prime focus
Elliptical, 1.1 m x 0.7 m (equivalent to 0.9 m circular)
58 um / arc sec
Collimated beam diameter
Elliptical, 22.2 mm x 14.5 mm
after M3
f/no at spectrometer input
20.5
Space
only)
1400 mm (z) x 950 mm (y) x 1200 mm (x)
envelope
(optics
10.3
15
Spectrometer Instrument
Dual Offner
spectrometers with
common focal plane
and grating ruling
density
SPECTROMETER INPUT CH1
M1 CH1
M2
COMMON FOCAL PLANE
FOR CH0 AND CH1
SPECTROMETER INPUT CH0
M1 CH0
M1 CH0
M1 CH1
G1 CH1
M2
SPECTROMETER
INPUT CH1
G1 CH0
COMMON FOCAL PLANE FOR CH0 AND CH1
SPECTROMETER INPUT CH0
16
Spectrometer Detector
– On-going contacts with CEA/LETI on
their progress
• Work is continuing within
consortium both on developing
concepts to allow detectors to run
warmer or to allow use of European
existing detectors – will continue
through phase A study.
CH1 MAX WAVELENGTH
CH0 MAX
WAVELENGTH
5.0 mm
8.0 mm
INCREASING WAVELENGTH
• Baselined NEOCam MCT detector
for proposal
• Know that work is on-going in
Europe on MCT devices out to ≥ 8
mm
6.3 mm
CH0 MIN
WAVELENGTH
CH1 MIN
WAVELENGTH
17
Instrument Control Unit
18
Fine Guidance System / NIRPhot
• Baseline is now a 4 channel FGS /
Photometer behind Gregorian
telescope
– Provides full redundancy in guidance
function
– Offset detectors in focus in opposite
directions and allow to use as ShackHartmann WFS in early commissioning
– Provides four channels of NIR
photometer to assist in decorrelating
spectrometer signals
• Exact optical design implementation
still to be iterated and agreed in
consortium
ARIEL M4 proposal
19
Potential Dichroic Definitions
Dichroic
Name
Purpose
Reflected l
(microns)
Transmitted l
(microns)
Com-D1
Division of FGS from
Spectrometer Channels
0.55 – 1.0
1.95 – 7.8
Com-D2
Sub-Division of Spectrometer
1.95 – 3.9
3.9 – 7.8
FGS-D3
Sub-Division of FGS Light to 2
bands
0.55 – 0.7
0.8 – 1.0
FGS-D4
Sub-Division of SW-NIRPhot
bands
0.55 – 0.62
0.62 – 0.7
FGS-D5
Sub-Division of LW-NIRPhot
bands
0.8 – 0.9
0.9 – 1.0
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FGS / NIRPhot Detectors
• Design baseline is European detector for this channel,
on-going developments at numerous manufacturers
• Data shows acceptable performance from existing
detectors in terms of dark current & noise, key factor
now getting sufficient sensitivity at shortest
wavelength end.
– Under consideration if the coverage down to 0.55 microns
is really necessary
• Back-up option of higher TRL (9) detectors from US
21
Thermal design
22
Coolers
•
•
Assuming that Coolers are required to ensure
sufficiently cold temperature for the
spectrometer detectors then baseline is
implementation of Neon JT cooler.
Believe that thermal requirements can be
satisfied by a (probably dual-stage) tactical
cooler compressor (developed by RAL /
Hymatic) converted to run as a JT.
– Study kicked off to consider the expected
performance in this case.
•
•
Backup would be the larger Neon JT cooler
system as baselined for EChO.
This can provide ~200 mW cooling at ~30 K
– Input power required: 95 W
– System mass: ~11.5 kg
– These numbers (worst-case) are assumed for the
budgets below
23
Payload Mass Budget
Item
CBE Mass - Baseline
(kg)
Nominal Mass Baseline (kg)
Cold Instrument Assembly
Spectrometer Optics Unit
FGS / NIR-Phot Optics Unit
Common Optics & Cal Module
Radiators
Payload Optical Bench
JT Cooler Cold Head
37.2
6
4
2
10.2
15
1.5
44.64
7.2
4.8
2.4
12.2
18.0
1.8
Telescope Assembly
M1 Mirror
M1 Mirror ISMs
M2 Mirror
M2 Refocus Mechanism
M3 Mirror
M3 Support structure
Baffle & Structure
84.3
27.8
1.8
1.5
3.8
0.2
1.5
47.7
100.8
33.4
2.2
1.8
4.2
0.2
1.8
57.2
6.5
7.8
30
3
27
17.5
10.5
7
8.1
36.0
3.6
32.4
21.0
12.6
8.4
9.7
Payload Cryo-harnesses
Thermal Shield Assembly
Top floor MLI & connections
V-Groove Assy & PLM Struts
Payload Warm Units
Instrument Control Unit (inc TCU)
FGS Electronics
Cooler Compressors & Plumbing
24
Payload Power Budget
Item
Basic Power (W)
Nominal Power (W)
Instrument Control Unit
37.5
45.0
FGS Control Unit
16.5
19.8
Cooler Electronics &
Compressors
80.0
95.0
• Note that contamination control heater lines not
included in baseline operational power budget.
• All dissipation within PLM would be drawn by one
of the warm payload units in the SVM.
25
Payload Data Rate Budget
Pixels
Spat.
Pixels Spect.
Bits per
Prim. Rate
Chan Total
sample
(Hz)
Science Channels
Int. time
per ramp
(sec)
No. Bits /
Total
GBits Per
ramp
Bits / sec
day
FGS
photometer
mode (x4)
32
32
1024
16
1/3
21485
1.76
FGS AOCS mode
AIRS-1
AIRS-2
1
16
16
16
8192
8192
21
16
16
10
10
10
3360
57344
57344
0.27
4.61
4.61
Total
16400
16
512
512
3
3
21
21
Total Sci (bits/sec) 139893
Total sci/day (Gbits)
Houskeeping Channels
11.26
Instrument
Temps
16
16
2
512
Electronics etc
32
12
2
768
M2 actuators
8
16
0.5
64
Heaters
8
16
0.5
64
Temps
32
16
2
Total HK bits/sec)
1024
2432.00 0.20
Grand total
11.4626
Contributors
UK
Italy
France
Spain
Belgium
Nederlands
Austria
Poland
Germany
Norway
27
Italian contribution
1. Telescope (mirrors, optical bench, baffles, bipods)
2. Instrument Control Unit (HW + SW)
3. Thermal design
4. Ground Segment
28
Overall M4 Timeline and
Milestones
29